To satisfy the requirements of small satellites with attitude control requirements, a guidance, navigation, and control module was designed at the Texas Spacecraft Laboratory. However, these small satellites tend to have attitude constraints in the form of keep-in and keep-out cones. Two methods for autonomous constrained attitude guidance are presented. The first satisfies the problem of guiding a single axis through keep-out constraints while satisfying a second keep-in constraint through an adjoined optimization routine. The method leverages methods for discretizing the attitude shell combined with the graph pathfinding algorithm A*. The second approach generalizes the problem to any number of attitude constraints in the body and inertial frame by discretizing the quaternion space using a series of concentric discretized shells. An approach for discretized attitude optimization is created to allow the vehicle to identify which attitude mode to operate under while simultaneously optimizing the solar power input. The discretized constrained attitude guidance and attitude optimization techniques are tied together in the flight software architecture and tested in a hardware-in-the-loop simulation environment. / text